Log positioning device and method

ABSTRACT

A method of positioning a log of sheet material includes sensing the presence of a log in a staging area having a length, a midpoint at the center of the length, and a boundary point between the midpoint and an end of the length; sensing the presence or absence of a portion of the log at the boundary point; and moving the log along the length of the staging area. When the log is present in both the staging area and at the boundary point, the log is moved toward the midpoint. When the log is present in the staging area and absent from the boundary point, the log is moved toward the boundary point.

BACKGROUND

[0001] Disposable sheet products such as paper towels, toilet tissue, and wet wipes have many applications. They may be used with small children and infants when changing diapers, they may be used for house hold cleaning tasks, they may be used for cleaning hands, they may be used as a bath tissue, they may be used by a caregiver to clean a disabled or incontinent adult, or they may be used in and for a whole host of other applications. Typically, these sheet products have been provided as a stack of separate sheets or as a roll of perforated sheets wound on a solid or hollow core.

[0002] Wet wipes have traditionally been made in processes in which larger webs of wipes are initially made, and then these larger webs are converted into smaller rolls or sheets that can be placed in a dispenser. Embodiments of dispensers are described in copending applications Ser. No. 09/545,995 filed Apr. 10, 2000; Ser. No. 09/565,227 filed May 4, 2000; Ser. Nos. 09/659,307; 09/659,295; 09/660,049; 09/659,311; 09/660,040; 09/659,283; 09/659,284 and 09/659,306, filed Sep. 12, 2000; Ser. No. 09/748,618, filed Dec. 22, 2000; Ser. No. 09/841,323, filed Apr. 24, 2001; Ser. No. 09/844,731, filed Apr. 27, 2001; and Ser. No. 09/849,935, filed May 4, 2001, all of which are commonly assigned to Kimberly-Clark, and the disclosures of which are incorporated herein by reference.

[0003] Wet wipes can be any wipe, towel, tissue or sheet like product including natural fibers, synthetic fibers, synthetic material and combinations thereof, that is wet or moist. Examples of wet wipes are disclosed in U.S. Pat. Nos. 6,423,804 B1; 6,429,261 B1; 6,444,214 B1; and in copending U.S. patent applications Ser. Nos. 09/564,449; 09/565,125; 09/564,837; 09/564,531; 09/564,268; 09/564,424; 09/564,780; 09/564,212; 09/565,623 all filed May 4, 2000; and Ser. No. 09/900,698, filed Jul. 6, 2001. All of these patents and patent applications are commonly assigned to Kimberly-Clark, and the disclosures of all these documents are incorporated herein by reference.

[0004] For sheet products that are provided in roll form, it may be desirable to form the individual rolls by separating the rolls from a log of rolled sheet material. Logs of rolled sheet materials may be produced by winding a large amount of sheet material into individual logs of roughly equal dimensions. The separation of rolls from a given log of material may then be accomplished, for example through the use of a saw that sequentially cuts rolls from the log from one end to the other, or through the use of a multi-blade saw that divides the log into multiple rolls simultaneously. Any variability or inconsistency in the log-forming process may impact the ability to produce consistent, high-quality individual rolls from the log saw.

[0005] There is thus a need for improved methods of making individual portions of wipes, particularly for making rolls of wet wipes. It is desirable that portions of wipes are produced in an automatic fashion to provide rolls having optimum quality, consistent dimensions, and uniform ingredients.

BRIEF SUMMARY

[0006] In an embodiment of the invention, there is provided a method of positioning a log of sheet material, comprising sensing the presence of a log in a staging area, the staging area comprising a length, a midpoint at the center of the length, and a boundary point between the midpoint and an end of the length; sensing the presence or absence of a portion of the log at the boundary point; and positioning the log relative to the boundary point.

[0007] These embodiments may further comprise a method wherein, when the log is present in both the staging area and at the boundary point, the positioning comprises moving the log along the length of the staging area toward the midpoint until the log is absent from the boundary point. These embodiments may yet further comprise a method wherein, when the log is present in the staging area and is absent from the boundary point, the positioning comprises moving the log along the length of the staging area toward the boundary point until the log is present at the boundary point

[0008] In another embodiment of the invention, there is provided a method of positioning a plurality of logs of sheet material, comprising providing a single log in a staging area, the staging area comprising a length, a midpoint at the center of the length, and a boundary point between the midpoint and an end of the length; sensing the presence or absence of a portion of the log at the boundary point; positioning the log relative to the boundary point; releasing the log from the staging area; and repeating the providing, sensing, positioning and releasing.

[0009] These embodiments may further comprise a method wherein the positioning comprises moving the log along the length of the staging area toward the midpoint when the log is present at the boundary point. These embodiments may yet further comprise a method wherein the positioning comprises moving the log along the length of the staging area toward the boundary point when the log is absent from the boundary point.

[0010] In another embodiment of the invention, there is provided a method of positioning a wet log of sheet material, comprising sensing the presence of a wet log in a staging area by measuring a signal from a first optical sensor, the staging area comprising a length, a midpoint at the center of the length, a boundary point between the midpoint and an end of the length, and a conveyor belt; sensing the presence or absence of a portion of the wet log at the boundary point by measuring a signal from a second optical sensor; and moving the wet log along the length of the staging area by cycling the conveyor belt, the moving of the wet log comprising cycling the wet log toward the midpoint until the wet log is absent from the boundary point, when the wet log is present in both the staging area and at the boundary point; or cycling the wet log toward the boundary point until the wet log is present at the boundary point, when the wet log is present in the staging area and is absent from the boundary point.

[0011] In another embodiment of the invention, there is provided an apparatus for positioning a log of sheet material, comprising a staging area comprising a length, a midpoint at the center of the length, and a boundary point between the midpoint and an end of the length; a first sensor positioned to detect the presence or absence of a log in the staging area; a second sensor positioned to detect the presence or absence of the log at the boundary point; and a conveyor belt positioned to cycle along the length of the staging area.

[0012] In another embodiment of the invention, there is provided an apparatus for positioning a log of sheet material, comprising means for supporting a log; means for detecting the presence or absence of a log on the supporting means; means for detecting the presence or absence of a portion of the log at a boundary point; and means for moving the log toward or away from the boundary point; wherein, when the log is detected as present both on the supporting means and at the boundary point, the moving means moves the log away from the boundary point; and when the log is detected as present on the supporting means but absent from the boundary point, the moving means moves the log toward the boundary point.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a diagram of a log forming apparatus.

[0014]FIG. 2 is a diagram of a log processing apparatus.

[0015]FIG. 3 is a diagram of a log saw apparatus.

[0016]FIG. 4 is a diagram of a log processing apparatus.

[0017]FIG. 5 is a perspective diagram of a multi-blade log saw.

[0018]FIG. 6 is a front diagram of a multi-blade log saw.

[0019]FIG. 7 is a diagram of a staging area.

[0020]FIG. 8 is a diagram of a log of material.

[0021]FIG. 9 is a perspective view of an individual roll of wound sheet material.

[0022]FIG. 10 is a diagram of a log of material and an optical sensor.

[0023]FIG. 11 is an end view diagram of a log of material and an optical sensor.

[0024] FIGS. 12A-D are diagrams of a log positioning apparatus.

[0025]FIG. 13 is a diagram of a log positioning apparatus connected to a log processing apparatus.

DETAILED DESCRIPTION

[0026] A method and apparatus for positioning a log of sheet material is provided which in general provides for adjusting the location of the log in a staging area. The positioning may allow the log to be located in an optimum position relative to an apparatus for processing or handling the log. The positioning involves detecting the presence of the log in the staging area, detecting the presence or absence of a portion of the log in a particular location of the staging area, and moving the log either toward or away from that particular location.

[0027] Logs which may be positioned include logs composed of one or more sheets of material such as paper, cloth, plastic, metal foil, and mixtures of these materials. A log may contain a single sheet that has been converted into log form, or it may contain more than one sheet. For example, a log may contain a single sheet which has been folded multiple times to provide a log in a form similar to a rectangular prism. In another example, a log may contain a single sheet which has been wound to provide a cylindrical log. In yet another example, a log may contain a plurality of sheets which are stacked to form a rectangular prism. In this example, the sheets can be stacked as flat sheets, or they be folded either with or without any overlap of the ends of the sheets.

[0028] A log of wound sheet material can be provided by a variety of methods. For example, individual logs may be produced by winding a sheet material as it is delivered from a sheet forming machine. In this example, it may be advantageous to use more than one winding machine, to allow the sheet to be formed continuously without slowing or stopping the sheet formation as a log is completed and removed from the winder. In another example, individual logs may be produced by unwinding a large roll of sheet material and rewinding the sheet into smaller logs.

[0029] For the production of rolls of wet wipes, the logs may be maintained in a dry condition for the entire process, including during the formation of individual rolls, and wet rolls may then be formed by soaking the individual rolls in a wetting solution. It may be desirable to provide the log in a moist condition before dividing it into individual rolls. Logs may be formed in a dry condition and then soaked in a wetting solution, or a wetting solution may be applied to the sheet before or during the winding of the log. It may be desirable to apply a wetting solution to the sheet prior to winding the sheet into moist logs, so as to provide uniform and consistent application of moisture and of the ingredients of the wetting solution. Individual stacks of wet wipes sheets may also be formed using similar strategies. Individual stacks may be formed from logs of stacked sheet material, and the moisture may be applied to the sheet material while it is in sheet form, in log form, or in individual stacks.

[0030] An example of an apparatus for forming wet logs of sheet material is illustrated in FIG. 1. A web of sheet material 2 may be any type of basesheet known to those skilled in the art. Sheet materials which are useful include fibrous webs, i.e. paper sheets. For example, a sheet material may be a nonwoven basesheet, such as a dry-formed basesheet or a wet-laid basesheet, including tissue and towel basesheets. A sheet material may be an airlaid, spun-laid, hydroentangled, spun-bond, or melt-blown (for example, coform) basesheet. A sheet material may be a multi-layer basesheet, such as a laminate of any combination of these basesheets. A sheet material may contain a binder, for example a non-dispersible binder, such as a latex binder or a cross-linkable binder; or a water-dispersible binder, such as a temperature-sensitve water dispersible binder or an ion-sensitive water dispersible binder. Ion-sensitive water-dispersible binders, such as those disclosed in the above-referenced co-pending patent applications, provide for water dispersibility of 80% or greater. Water dispersibility is defined as: 1 minus (the cross-direction wet tensile strength in water, divided by the original cross-direction wet tensile strength of the wet wipe), multiplied by 100%.

[0031] The term “nonwoven” means a web having a structure of individual fibers or threads which are interlaid, but not in a regular or identifiable manner as in a knitted fabric. Nonwoven fabrics or webs may be formed from many processes including, for example, meltblowing processes, spunbonding processes, air laying processes, and bonded carded web processes.

[0032] The term “coform” refers a process in which at least one meltblown diehead is arranged near a chute through which other materials are added to the web while it is forming. Such other materials may be pulp, superabsorbent particles, natural polymers (for example, rayon or cotton fibers) and/or synthetic polymers (for example, polypropylene or polyester) fibers, for example, where the fibers may be of staple length. Coform processes are described in U.S. Pat. Nos. 4,818,464 and 4,100,324, which are both commonly assigned to Kimberly-Clark. Webs produced by the coform process are generally referred to as coform materials.

[0033] An example of a useful sheet material is Kimberly-Clark Supreme Care™ baby wipes (KIMBERLY-CLARK CORPORATION, Neenah, Wis.), as described U.S. patent application Publication No. US 2002/0127937 A1, which is commonly assigned to Kimberly-Clark, and which is incorporated herein by reference. This type of basesheet contains coform blended with polypropylene fibers and fluff. Other examples of individual webs include a melt-blown basesheet with a latex binder; a spun-bond basesheet with a temperature-sensitve water dispersible binder; and an airlaid basesheet with an ion-sensitve water dispersible binder. The web may be delivered to a wetting and winding apparatus 1 as a sheet of material. The web may be unwound from a roll, or it may be fed to the apparatus directly from a web making apparatus. The web may be a single sheet, or the web may have multiple sheets that are combined to form a multi-ply sheet. Multi-ply sheets may be bonded together, for example with adhesives, thermal bonding, sonic bonding, or hydroentanglement. The web may contain perforations, which may desirably be lines of perforations at regular intervals, and these perforations may be introduced during the web making process or during subsequent processing of the sheet. For example, a perforating apparatus as described in U.S. Pat. No. 5,125,302, incorporated herein by reference, may be used to perforate the web.

[0034] In one example, referring to FIG. 1, the web 2 may be dispensed from a parent roll 4 which can be mounted on a rotating shaft 6. The unwinding of the roll can be controlled such that the web is dispensed at a consistent speed and tension even though the size of the roll is decreasing. The web in sheet form may be delivered in the direction of arrow 20 to the wetting apparatus 35. The speed of the web may be at least 60 meters per minute (m/min). It may be desirable for the speed of the web to be at least 80 m/min; more desirably at least 150 m/min; more desirably still at least 300 m/min; more desirably still at least 500 m/min; more desirably still at least 700 m/min; more desirably still at least 1000 m/min. A wetting solution may be applied to the web by wetting apparatus 35, and the wet web is then delivered to a wet winding apparatus 41 to provide log 100 of moist, wound sheet material. Careful handling of the wet web may be desirable, since the presence of moisture in the web can alter the physical properties of the material. For example, incorporation of 225% by weight of a wetting solution can increase the percent elongation at failure (i.e. “stretch”) of a web from 5-10% to 25-40%. In general, the strength of the web is also decreased upon application of a given wetting solution.

[0035] It is desirable that the wet winding apparatus can provide for continuous winding of wet logs. It is also desirable that each log produced by this apparatus under a given set of conditions has substantially the same number of sheets (as defined by lines of perforations) and substantially the same dimensions. Useful wet winding apparatus may be any winding apparatus known to those skilled in the art. The wet winding apparatus may, for example, wind a web around a removable mandrel to produce a coreless material (U.S. Pat. Nos. 5,387,284; 5,271,515; 5,271,137; 3,856,226). The winding apparatus may, for example, wind a web around a tubular or cylindrical core (U.S. Pat. Nos. 6,129,304; 5,979,818; 5,368,252; 5,248,106; 5,137,225; 4,487,377). The winding apparatus may, for example, be a coreless surface winder which can produce coreless rolls without the use of a mandrel. (U.S. Pat. Nos. 5,839,680; 5,690,296; 5,603,467; 5,542,622; 5,538,199; 5,402,960; 4,856,725). The above patents are incorporated herein by reference. Further examples of wet winding apparatus for providing wet coreless logs are provided in copending applications Ser. Nos. 09/900,516 and 09/900,746, filed Jul. 6, 2001; Ser. No. 09/989,829 filed Nov. 19, 2001; Ser. No. 10/024,999 filed Dec. 18, 2001; and Ser. No. 10/036,863 filed Dec. 21, 2001; all of which are commonly assigned to Kimberly-Clark. These copending applications are all incorporated herein by reference.

[0036] Examples of wetting solutions are given in the above mentioned U.S. Pat. Nos. 6,423,804 B1; 6,429,261 B1; 6,444,214 B1; and in copending U.S. patent applications Ser. Nos. 09/564,449; 09/565,125; 09/564,837; 09/564,531; 09/564,268; 09/564,424; 09/564,780; 09/564,212; 09/565,623; and 09/900,698. The amount of liquid or wetting solution contained within a given wet web can vary depending on factors including the type of basesheet, the type of liquid or solution being used, the wetting conditions employed, the type of container used to store the wet wipes, and the intended end use of the wet web. Typically, each wet web can contain from about 25 to about 600 weight percent and desirably from about 200 to about 400 weight percent liquid based on the dry weight of the web. To determine the liquid add-on, first the weight of a portion of dry web having specific dimensions is determined. The dry web corresponds to the basesheet which can be fed to the wetting and winding apparatus. Then, the amount of liquid by weight equal to a multiple (e.g. 1, 1.5, 2.5, 3.3, etc., times) where 1=100%, 2.5=250%, etc., of the portion of the dry web, or an increased amount of liquid measured as a percent add-on based on the weight of the dry web portion, is added to the web to make it moistened, and then referred to as a “wet” web. A wet web is defined as a web which contains a solution add-on between 25% and the maximum add-on which can be accepted by the web (i.e. saturation). It may be desirable for the wetting solution add-on to be between about 25% and 700%; between 50% and 400%; between 100% and 350%; between 150% and 300%; or between 200% and 250%.

[0037] Due to the nature of any log formation process, especially winding processes involving moist sheet materials, the final logs may have some inconsistencies. For example, the amount of basesheet and/or wetting solution in the final log may vary between logs. Some of this variation may be the result of inconsistency in the formation of the initial basesheet, the composition, thickness, and density of which may vary from the center of the sheet to the edges. Some of the variation may also result from inconsistency in the amount of wetting solution applied, inhomogeneity of the wetting solution, or inconsistency in the absorbancy of the basesheet. Furthermore, if the wet winding process is not completely precise, the total sheet area of the log may vary between logs. The term “total sheet area” refers to the total area of the sheet or sheets when they are laid flat.

[0038] The shape of the ends of the log may vary between logs. This type of inconsistency may be due to the sources of variation mentioned above and/or to other sources of variation. For example, the stresses imposed on the web during a winding process can distort the web from its initial dimensions. Wet webs are especially sensitive to this distortion, and can be stretched out, or “extruded,” during a winding process. Thus, in the case of wet coreless logs the winding process may form tapered shapes on one or both ends of the log due to the forces imposed on the sheet during the winding process. Furthermore, the position of the logs as collected or delivered from the log forming apparatus may be inconsistent. For example, the logs may not be in exact alignment with each other.

[0039] These inconsistencies can cause problems in the subsequent processing of the logs. For example, if the logs are intended to be cut into individual stacks or rolls, the inconsistencies can result in the production of stacks or rolls which do not have the desired dimensions, causing these non-uniform items to be disposed of as scrap. In another example, it the logs are intended to be packed together for storage or shipment, the inconsistencies can result in packing which is not optimum, causing damage to some of the logs or causing potential packing space to be wasted. In yet another example, logs may be processed by marking, for example by printing or embossing, or by application of additives in a pattern. Inconsistencies in the shape or placement of the logs can result in misalignment of the markings and/or additives from their intended locations.

[0040] The precise and consistent positioning of logs of sheet material can thus provide for increased consistency of the final intended product. Once a staging area is properly aligned with the processing or handling apparatus, each log can be positioned in the desired location such that the log interacts as intended with the processing or handling apparatus. A log which is provided in the staging area, for example after being dispensed from a log forming machine, can be misaligned and/or may have ends which are not uniform. Such a log can still be processed into the desired final product once it has been positioned to the proper location within the staging area.

[0041] An example of a log processing apparatus which may benefit from the consistent, automatic positioning of logs of sheet material is a log saw apparatus. A log saw is an apparatus which can divide a log of material into smaller units, desirably in a single cutting step. A log of wound material can be cut into individual rolls during a single interaction of the log with the saw. Likewise, a log of stacked sheets can be cut into individual stacks during a single cutting step. Examples of log saws are provided in copending applications Ser. Nos. 09/747,594 and 09/748,616, filed Dec. 22, 2000; and Ser. No. 10/003,454, filed Oct. 31, 2001; all of which are commonly assigned to Kimberly-Clark. These copending applications are incorporated herein by reference. It may be desirable for a log saw apparatus to divide low rigidity substrate logs, such as moistened logs, into rolls. The use of this type of apparatus may minimize distortion of the finished product, especially in terms of shape and cut squareness, and may thus be used to process moistened product.

[0042] In one example of the use of a log saw to process a log of material, a wound log of wet wipes may be cut into individual rolls of wet wipes. A log of wound moist sheet material from which rolls may be cut may have a diameter between 50 mm and 160 mm, desirably between 55 mm and 130 mm, desirably between 65 mm and 100 mm, and desirably about 71 mm. When unwound into a sheet, the length of the resulting sheet may be between 300 inches (8 m) and 1000 inches (25 m), desirably between 400 inches (10 m) and 800 inches (20 m), desirably about 440 inches (11.2 m). The wound log has a length along its longitudinal axis between about 2440 mm to 3050 mm, desirably 2540 mm to 2900 mm, and desirably about 2616 mm. Such a log of wound moist sheet material may be formed by the wet winding methods and apparatus described above.

[0043] As shown in FIG. 2, an apparatus 1 may be used to cut an entire log 100 of substrate into individual rolls 102. In this example, logs are delivered into a distribution sprocket 11 and are transported in a direction perpendicular to the longitudinal axis of the log. The pockets 15 in the distribution sprocket are shaped to hold logs during the cutting operation without the need to use a secondary clamping device. A log which is nested into the sprocket is supported along its entire length and rotated into a cutting area 80 (FIG. 3) where it is divided into rolls by a cutting device, such as a multi-blade rotary saw 81 having a common axis 54. The divided log is rotated past the cutting area, and the individual rolls are secured in the pockets by a roll retention device 25. The retention device prevents the rolls from leaving the pockets until the desired roll exit point 56 is reached. Unwinding and scuffing of the rolls is also prevented by the retention device. The rolls may be deposited on a diverter 34 which then delivers the rolls to an index conveyor 33 for further processing. Since the substrate is secured during the cutting procedure, there is no need for a spindle or mandrel to be used for roll products. Thus, coreless rolls of wipes, including wet wipes, can be cut precisely by this apparatus.

[0044] Referring again to FIG. 2, the logs may be delivered initially to an infeed conveyor 13. The delivery may be metered if necessary, such as by a controllably movable gate 26. The conveyor, which is desirably made of 316L stainless steel, is mounted on a frame 17. The conveyor may be movably mounted such that it can be in a lowered position 72 during use or can be in a raised position 74 for maintenance or cleaning. The conveyor may be mounted to the frame by support arms 73, which are connected to servo motors 71. These support arms raise or lower the conveyor in response to a signal from an actuator. The infeed conveyor is equipped with concave holders 19 that cradle the logs and prevent them from falling off the conveyor. The holders are preferably shaped as shown in FIGS. 2 or 4 with planar walls and a curved bottom. This configuration allows the roll to be dropped into the holder in a vertical manner, rather than rolling in at an angle. The optional metering gate 26 can also assist in assuring this vertical delivery. Holders of different dimensions and configurations may be employed for different substrates, and the conveyor may be equipped to support a variety of interchangeable holders.

[0045] When a log reaches the end of conveyor 13, it is transferred to an apparatus for cutting the log. Referring to FIGS. 2 and 3, the cutting apparatus of this example includes a distribution sprocket 11, which rotates the log in the direction of arrow 64 into the cutting area 80. The log is divided in the cutting area, and the sprocket rotates the divided roll away from the cutting area to allow for collection of the individual rolls. The sprocket is mounted on a frame 41 and rotates on a rotating shaft 82. The sprocket has multiple pockets 15, each of which can hold one log of material at a time. Referring to FIG. 5, each pocket has a multiplicity of channels 32 configured so as to allow the blades of the saw to pass through them in the cutting area. It is desirable that the channels are narrow enough to provide sufficient support for the substrate, yet wide enough to allow the blade to pass through and to allow for thorough cleaning of the sprocket.

[0046] In the example illustrated in FIG. 6, the saw 81 comprises a plurality of circular blades 16. The number of blades depends on the number of individual rolls desired and is greater than the number of rolls. As illustrated, the saw in this example has 26 total blades, 13 each on shafts 42 and 44, form two cutting assemblies. These two assemblies together can produce 25 rolls of the desired dimensions from one log. Examples of circular saw blades include those available from ORBITAL SAW CO, INC. The model 412034 is a nickel plated blade made of D-2 high-chrome tool steel, with a 24 inch (610 mm) diameter, 3.25 inch (82.6 mm) inner diameter (ID) bore, and a 0.150 inch (3.81 mm) thickness. The spacing 46 between the blades is 4 inches (10.2 cm). The blade diameter of 20-24 inches (508-610 mm) provides for complete cutting of a log having a diameter of 71 mm while ensuring clearance of the blade shaft. The blades may operate at a variable speed between 1500 rpm and 1700 rpm, which can be helpful in minimizing vibrations in the apparatus. The log saw of this example, when separating each log into 25 rolls, may be operated at a speed sufficient to produce at least 200 rolls per minute, and may further produce at least 400 rolls per minute, or 700 rolls per minute. Higher or lower production speeds may be optimal for logs of different dimensions and/or containing different types of sheet material.

[0047] The spacing 46 of the blades relative to each other determines the size of the individual rolls produced. It follows that the consistency of this spacing affects the consistency of the product. Also, the spacing and configuration of the blades relative to the dimensions of the log affects the amount of waste produced by cutting the log. If the log is longer than the end-to-end distance of the array of blades, one or both ends may produce rolls which are too small to be of commercial value. The ends, referred to as “trim,” are waste material and are typically disposed of. It is desirable to reduce the size of the trim portions, or to eliminate them if possible, so as to reduce the overall waste of the production. To the extent that trim is not eliminated, it may be necessary to remove the trim from the log saw, such as by way of a chute. The chute may deliver the trim directly to a container for discarding or recycling, or the chute may deliver the trim to a conveyor that removes it from the apparatus.

[0048] The position of a log in a desired location, or within a desired range of locations, can provide for improved consistency in the subsequent processing of the log. In the example of the log saw processing described above, the position of the log can affect the size of the trim from the ends of the log. The precise positioning of the log can ensure that the maximum number of individual stacks or rolls are produced from a log, and it can also ensure that the trim produced has a size that is within a particular range. Consistency in the size range of the trim produced can be beneficial in that it can allow for consistent behavior of the trim during any trim removal processes. It is desirable that a relatively small portion of the substrate log is cut from each end of the log by the outermost saw blades, such that the trim accounts for less than 10%, less than 5%, or between about 1% and 3% of the total length of the log.

[0049] The positioning of a log into a desired location may occur at various points in the production process. For example, the positioning may occur immediately after the log is formed. In another example, the positioning may occur immediately prior to the processing of the log. In either of these cases, a positioning apparatus may be in direct contact with the log forming machine and/or the log processing machine, or it may be physically attached to one or both of the machines. In yet another example, the positioning may occur at some intermediate point between the forming of the log and the processing of the log. In the above example of the log saw processing machine, for example, a positioning apparatus may be located at the bottom of the infeed conveyor or at the top of the infeed conveyor. In many cases, it is desirable to position the log immediately prior to the processing of the log to minimize the opportunities for misalignment of the log between the positioning and the processing.

[0050] The positioning method is carried out in a staging area. Referring to the example of FIG. 7, a staging area 200 can have a length 202 and a width 204. Comparing FIG. 7 to FIG. 8, it is desirable that the dimensions of the length and width are at least as large as the length 224 and width 222 of the log. The length of the staging area has a midpoint 208 at the center of the length. The length of the staging area also has two ends 206 at the termini of the length, and a boundary point 210 between the midpoint and one of the ends. The boundary point serves as the reference point for positioning the end of the log, and the midpoint serves as the reference point for the direction of motion of the log during the positioning process.

[0051] The method includes detecting the presence of a log in the staging area, detecting whether a portion of the log is at the boundary point, and moving the log accordingly. If a log is in the staging area and is also detected at the boundary point, the log is automatically moved toward the midpoint of the staging area. The movement of the log continues until the log is no longer detected at the boundary point. In contrast, if a log is in the staging area but is not detected at the boundary point, the log is automatically moved toward the boundary point and away from the midpoint. In this case, the movement of the log continues until the log is detected in the boundary point. Thus, the final position of the log is substantially the same, whether the log is initially present in or absent from the boundary point. The precision of the final position of the log is dependent on how quickly the movement of the log is stopped when the necessary detection is complete.

[0052] The detection of the log in the staging area can be accomplished by a variety of methods. For example, the staging area may have a mechanical switch that is changed from one state to another state when a log enters the staging area and depresses the switch. In another example, the staging area may be connected to a device for measuring the mass of a substance in the area. For example, the staging area may be connected to an electronic balance or to a piezoelectric device. In yet another example, the presence of the log can be detected by an optical sensor or an ultrasonic sensor. For example, an optical sensor or an ultrasonic sensor may be configured to detect the presence or absence of a substance within a given volume of space.

[0053] The detection of the presence or absence of the log in the boundary point can also be accomplished by applying these same methods to the boundary point in a localized manner. For example, a mechanical switch may be positioned at the boundary point. In another example, a balance or piezoelectric device may be configured such that it only senses mass changes at the boundary point and/or in an area past the boundary point and away from the midpoint. In yet another example, an optical or ultrasonic sensor may be configured to detect the presence or absence of a substance at the boundary point.

[0054] It may be desirable for the log to be detected by optical sensors, since the equipment for this type of sensing is relatively easy to obtain, to use, and to replace. An optical sensor may detect an object that passes between a light emitter and a light receiver (opposed mode), it may detect an object that passes between a combined emitter/receiver and a reflective target (retroreflective mode), or it may detect an object that passes through a beam of emitted light within a given distance of a combined emitter/receiver (proximity mode). It may be desirable to use an optical sensor in a proximity mode so as to minimize the number of components used and to simplify the installation and alignment of the sensor, especially if sensors may need to be replaced in the course of long term operation. It may further be desirable to operate an optical sensor in a convergent proximity mode, which aligns the focal point of the emitter and receiver elements of the sensor. An optical sensor operating in a convergent proximity mode can be used to specifically detect the presence or absence of objects within a small range of locations.

[0055] A wide variety of optical sensors can be used to detect the presence of a log or of a portion of a log. Specific examples of optical sensors include sensors available from BANNER ENGINEERING CORP., Minneapolis, Min., such as models PD49VP6C200Q and Q45BB6FQ5. Optical sensors may be configured and used as recommended by the manufacturer, or they may be modified as needed. For example, it may be desirable to cover at least a portion of the optical sensor with a waterproof covering or a splash shield to minimize the exposure of the sensor to moisture. It may also be desirable to provide waterproof sealing around any openings, connections, or fittings. One or more coatings may also be applied to at least a portion of the sensor, such as moisture-resistant coatings, thermal insulating coatings, electromagnetic shielding coatings, and anti-fog coatings.

[0056] The movement of the log within the staging area is accomplished in response to the initial location of the log as measured by the two detectors. The log may be pushed along its length, for example by the force of a shoe that is actuated by a servo motor or actuated by a pneumatic or hydraulic system. The log may also be gripped at one or more locations along its length, for example by a set of clamps, such that the movement of the clamps provides the movement of the log. These methods may not be desirable for some log configurations and/or for logs made of certain substrates. For example, a premoistened log could be damaged by the frictional forces encountered in pushing the log along its length, or by the pressure exerted by clamps. Logs having low rigidity, including premoisted logs, and logs having non-uniform ends may also be difficult to move precisely through these methods.

[0057] In order to accommodate as wide a variety of logs as possible, it may be desirable to move the log within the staging area with a conveyor. For example, a conveyor may be configured to cycle in either direction along the length of the staging area. It is desirable that the length of the conveyor is greater than the length of the log to be positioned, and further is greater than the length of the log plus the possible variation in location along the length of the staging area when the log initially arrives in the staging area. The conveyor may be flat, or it may be concave to provide some stabilization to the log during the positioning process. It may be desirable for the belt on the conveyor to be made of a corrosion resistant metal, plastic, or cloth. In one example, the conveyor belt is made of polyurethane that is molded to have a curved center.

[0058] Logs which can be positioned may have well-defined dimensions. For example, referring to FIG. 8, the width 222 of the log 220 may be constant along the entire length 224 of the log. For circular logs, the width is the same as the diameter. In another example, the ends of the log may be normal to the axis of the log, such that the ends are flat and form a well-defined edge. Logs may, however, be positioned even if they are irregularly shaped. For example, the width of the log may vary from one end of the log to the other. In another example, one or both ends of the log may be irregularly shaped, as illustrated in FIG. 8. In this case, the log is considered to have a center portion 234 having a uniform log width, and an end portion 230, over which the width of the log is reduced from the log width 222 to zero. The bulk of the log between the end portions is referred to as the central portion in this case. Irregular end portions may result from a variety of factors, including irregularities in the shape or composition of the original basesheet, the log manufacturing process, or the processing, handling and/or storage of the log prior to its arrival at the staging area. The dashed lines 235 illustrate where the log may be divided, for example by a multi-blade log saw, to produce individual rolls 102. An example of an individual roll is shown in FIG. 9.

[0059] In a simplistic illustration, an end portion of a log can be represented as a cone of material at the terminus of a cylinder of the material. Referring to FIGS. 10 and 11, an optical sensor 240 intended to detect the presence or absence of a log in the boundary point can be configured to have a focal point 242 that is past the width edge 228 of the log 220 by a certain distance 250. Thus, the sensor will detect the log if the optical path intersects the log at point 242 and at points along the central portion of the log. This same configuration will detect the absence of the log if the optical path either fails to intersect the log entirely, or if the path intersects the log at the end portion at points away from point 242. Referring to FIG. 11, the focal point 242 may practically be any point along the line of view of the sensor that is within the distance of a focal window 243. The focal window is determined by the actual field of view of the sensor. If an optical sensor having a focal point is used to detect the presence or absence of a log at the boundary point, the focal point is the same as the boundary point.

[0060] Referring still to FIG. 10, an optical sensor 260 intended to detect the presence or absence of a log in the staging area generally can be configured with a view along the length of the staging area. A log 220 in the staging area thus intersects the line of view 262, allowing the sensor to detect the presence of the log. The optical sensor 260 may have a narrow field of view along line 262, or its field of view may be wider than, but centered generally around, the line of view. The configuration of the sensor may be modified and optimized to ensure that a non-uniform end of a log will not produce an inaccurate optical measurement, i.e. a measurement of an absence of a log when the log is actually present in the staging area.

[0061] An apparatus for positioning a log of sheet material according to this method includes a staging area, detectors for measuring the presence or absence of a log within the staging area and at the boundary point, and a device for moving the log in response to the measurements. The apparatus may also contain any microprocessors, relays, and software necessary to provide communication between the detectors and the moving device; however, these components may also be present in the log forming apparatus and/or the log processing apparatus. It may be desirable for the forming, positioning and processing of the log to be coordinated by a single set of controls.

[0062] An example of an apparatus 300 for positioning a log of sheet material is provided in FIGS. 12A through 12D. The apparatus includes a conveyor belt 310 operating between a drive pulley 315, which is operated by servo motor 317, and an idler pulley 320. The conveyor belt supports the log of sheet material and helps to define the staging area. The coordinated action of the pulleys cycles the belt toward one pulley or the other. The pulley and belt assembly are mounted on brackets 330 and 340. An optical sensor 350 for detecting the presence or absence of a log in the staging area is shown as mounted on bracket 340, but could also be mounted on either bracket. Likewise, an optical sensor 360 for detecting the presence or absence of a log at the boundary point is shown as mounted on bracket 330, but could be on either bracket. The staging area is represented in dashed lines as 390. The brackets may be connected to frame 370 to facilitate connecting the apparatus to another machine, such as a log forming machine or a log processing machine.

[0063] In a further example, FIG. 13 illustrates a positioning apparatus 300 connected to the distribution sprocket 11 of a multi-blade log saw, by way of frame 370. In this configuration, the positioning apparatus can receive a log of sheet material from the infeed conveyor 13. The log is held in place by movable gate 380, which keeps the log in the staging area during the positioning process and then moves to release the log into the sprocket. The movement of the gate is coordinated with the timing of both the infeed conveyor and the sprocket to allow for continuous production of individual stacks or rolls of wipes. As illustrated, this example is especially useful for wound logs of sheet material, as the angled orientation of the apparatus allows the wound log to roll into and out of the staging area. The rotational motion of the wound log desirably inhibits any unwinding of the log by providing for the direction of motion of the tail of the wound sheet to be opposite the direction of overall motion of the roll itself when the tail is in contact with the surface.

[0064] A positioning apparatus can be configured to accept logs formed from a wet winder, as described above, and to move the logs as necessary into a position that is optimized for the processing of the logs by a multi-blade log saw, as described above. The boundary point in this example is a certain distance “L” beyond the last blade of the saw, away from the midpoint of the staging area, and can be calculated by the following equation:

L=(Total log length−sum of individual roll lengths)/2;

[0065] The total log length is the minimum length dimension for a useable log, and corresponds to length 234 in FIG. 8. The sum of individual roll lengths corresponds to length 244 in FIG. 8. For logs having a minimum length of 2616 mm and intended to produce 25 rolls of 102 mm lengths, the boundary point of the staging area is 33 mm from the last blade of the log saw (distance “L”), which corresponds to a distance of 1308 mm from the midpoint of the staging area. The optical sensor used to detect the log at the boundary point has a focal point 5 mm beyond the edge of the log width. It is desirable that the positioning, including both detections and the necessary movement of the log, occurs in 2 seconds or less, or in 1.5 seconds or less. This speed of operation allows for a log processing rate of 30 logs per minute, which translates into a roll production rate of 750 rolls per minute. It is desirable that at least 10 logs may be processed per minute, and is more desirable that at least 20 logs may be processed per minute. The trim produced when using this configuration will have a width between 32.5 mm and 65 mm.

[0066] It should be noted that the staging area can be mobile or stationary. It is desirable for the sake of simplicity to use a stationary staging area to help keep the components of the apparatus in their proper orientation. In some cases, however, it may be desirable to use a mobile staging area. For example, the positioning apparatus may include a conveyor having multiple staging areas, each associated with a separate group of detection devices and positioning conveyor. In this way, logs can be continuously positioned as they are transported to the processing machine.

[0067] If the positioning apparatus is used with moist logs, it is desirable that the materials used for the apparatus are resistant to corrosion. The apparatus and their components may also be coated with corrosion resistant materials. Examples of corrosion resistant materials include 316L stainless steel, nickel and its alloys, tungsten carbide, and poly(tetrafluoroethylene) (TEFLON, DUPONT, Wilmington, Del.). The components of the apparatus may be controlled by standard controlling equipment and software. For example, the apparatus may be controlled and monitored with a standard programmable logic controller (PLC), which in turn may interface with a Human Machine Interface (HMI) such as a PANELMATE HMI (EATON Corp., Columbus, Ohio).

[0068] The positioning of logs of sheet material can thus be accomplished in a consistent and automatic manner. The consistency of positioning can allow for consistent processing of the log, and the automatic nature of the positioning can provide for rapid throughput of logs, as well as a minimization of operator error. The positioning of logs can be performed in a relatively small space, thus providing for straightforward connection of a positioning apparatus to a log forming machine and/or a log processing machine. The logs which can be positioned may have a variety of potentially problematic features, such as high moisture content, non-uniformity of shape, and low rigidity. 

1. A method of positioning a log of sheet material, comprising: sensing the presence of a log in a staging area, the staging area comprising a length, a midpoint at the center of the length, and a boundary point between the midpoint and an end of the length; sensing the presence or absence of a portion of the log at the boundary point; and positioning the log relative to the boundary point.
 2. The method of claim 1, wherein, when the log is present in both the staging area and at the boundary point, the positioning comprises moving the log along the length of the staging area toward the midpoint until the log is absent from the boundary point.
 3. The method of claim 1, wherein, when the log is present in the staging area and is absent from the boundary point, the positioning comprises moving the log along the length of the staging area toward the boundary point until the log is present at the boundary point.
 4. The method of claim 1, wherein the staging area comprises a conveyor belt, and the positioning further comprises cycling the conveyor belt.
 5. The method of claim 1, further comprising providing the log in the staging area prior to sensing the presence of the log in the staging area.
 6. The method of claim 1, further comprising releasing the log from the staging area after positioning the log relative to the boundary point.
 7. The method of claim 1, wherein the sensing the presence of the log in the staging area comprises measuring a status of a switch.
 8. The method of claim 1, wherein the sensing the presence of the log in the staging area comprises measuring a mass of a substance in the staging area.
 9. The method of claim 1, wherein the sensing the presence of the log in the staging area comprises measuring a signal from an ultrasonic sensor.
 10. The method of claim 1, wherein the sensing the presence of the log in the staging area comprises measuring a signal from an optical sensor.
 11. The method of claim 1, wherein the sensing the presence or absence of a portion of the log at the boundary point comprises measuring a status of a switch.
 12. The method of claim 1, wherein the sensing the presence or absence of a portion of the log at the boundary point comprises measuring a mass of a substance at the boundary point.
 13. The method of claim 1, wherein the sensing the presence or absence of a portion of the log at the boundary point comprises measuring a signal from an ultrasonic sensor.
 14. The method of claim 1, wherein the sensing the presence or absence of a portion of the log at the boundary point comprises measuring a signal from an optical sensor.
 15. The method of claim 14, wherein the log comprises a center portion and an end portion, the center portion comprising a width edge, and the optical sensor having a focal point which is positioned past the width edge.
 16. The method of claim 15, wherein the focal point is positioned from about 1 millimeter to about 20 millimeters past the width edge.
 17. The method of claim 15, wherein the focal point is positioned from about 2 millimeters to about 10 millimeters past the width edge.
 18. The method of claim 15, wherein the optical sensor has a focal window comprising the focal point.
 19. The method of claim 15, wherein the end portion has a uniform width equal to the width of the center portion.
 20. The method of claim 15, wherein the end portion has a non-uniform width.
 21. The method of claim 1, wherein the log comprises a wetting solution add-on of at least 25%.
 22. A method of positioning a plurality of logs of sheet material, comprising: providing a single log in a staging area, the staging area comprising a length, a midpoint at the center of the length, and a boundary point between the midpoint and an end of the length; sensing the presence or absence of a portion of the log at the boundary point; positioning the log relative to the boundary point; releasing the log from the staging area; and repeating the providing, sensing, positioning and releasing.
 23. The method of claim 22, wherein the positioning comprises moving the log along the length of the staging area toward the midpoint when the log is present at the boundary point.
 24. The method of claim 22, wherein the positioning comprises moving the log along the length of the staging area toward the boundary point when the log is absent from the boundary point.
 25. The method of claim 22, wherein the providing comprises sensing the presence of the log in the staging area.
 26. The method of claim 22, wherein the length of the staging area is at least as long as an average length of a plurality of logs.
 27. The method of claim 22, wherein the providing comprises dispensing the single log from a storage area comprising a plurality of logs.
 28. The method of claim 22, wherein the providing comprises dispensing the single log from a log forming apparatus.
 29. The method of claim 28, wherein the log forming apparatus is an apparatus for wetting and winding a sheet of material.
 30. The method of claim 22, wherein the providing comprises transporting the single log toward the staging area and depositing the single log in the staging area.
 31. The method of claim 30, wherein the transporting comprises dispensing the single log onto a conveyor.
 32. The method of claim 22, wherein at least 10 logs are positioned each minute.
 33. The method of claim 22, wherein at least 20 logs are positioned each minute.
 34. The method of claim 22, wherein at least 30 logs are positioned each minute.
 35. The method of claim 22, wherein the sensing the presence or absence of a portion of the log at the boundary point comprises a member selected from the group consisting of measuring a status of a switch, measuring a mass of a substance at the boundary point, measuring a signal from an ultrasonic sensor, and measuring a signal from an optical sensor.
 36. The method of claim 25, wherein the sensing the presence of the log in the staging area comprises a member selected from the group consisting of measuring a status of a switch, measuring a mass of a substance in the staging area, measuring a signal from an ultrasonic sensor, and measuring a signal from an optical sensor.
 37. A method of positioning a wet log of sheet material, comprising: sensing the presence of a wet log in a staging area by measuring a signal from a first optical sensor, the staging area comprising a length, a midpoint at the center of the length, a boundary point between the midpoint and an end of the length, and a conveyor belt; sensing the presence or absence of a portion of the wet log at the boundary point by measuring a signal from a second optical sensor; and moving the wet log along the length of the staging area by cycling the conveyor belt, the moving the wet log comprising cycling the wet log toward the midpoint until the wet log is absent from the boundary point, when the wet log is present in both the staging area and at the boundary point; or cycling the wet log toward the boundary point until the wet log is present at the boundary point, when the wet log is present in the staging area and is absent from the boundary point.
 38. An apparatus for positioning a log of sheet material, comprising: a staging area comprising a length, a midpoint at the center of the length, and a boundary point between the midpoint and an end of the length; a first sensor positioned to detect the presence or absence of the log in the staging area; a second sensor positioned to detect the presence or absence of a log at the boundary point; and a conveyor belt positioned to cycle along the length of the staging area.
 39. The apparatus of claim 38, wherein the first sensor comprises an optical sensor having a field of view along the length of the staging area.
 40. The apparatus of claim 38, wherein the second sensor comprises an optical sensor having a focal point at the boundary point.
 41. The apparatus of claim 40, wherein, when a log comprising a width edge is in the staging area, the focal point is positioned past the width edge.
 42. The apparatus of claim 38, wherein, when the first sensor detects the presence of a log in the staging area and the second sensor detects the presence of a portion of the log at the boundary point, the conveyor belt cycles to move the log toward the midpoint until the log is absent from the boundary point.
 43. The apparatus of claim 38, wherein, when the first sensor detects the presence of a log in the staging area and the second sensor detects the absence of a portion of the log at the boundary point, the conveyor belt cycles to move the log toward the boundary point until the log is present at the boundary point.
 44. The apparatus of claim 38, wherein the staging area is connected to a log processing machine.
 45. The apparatus of claim 38, wherein the staging area is connected to a log forming machine.
 46. The apparatus of claim 38, further comprising a movable gate which can release the log from the apparatus.
 47. An apparatus for positioning a log of sheet material, comprising: means for supporting a log; means for detecting the presence or absence of a log on the supporting means; means for detecting the presence or absence of a portion of the log at a boundary point; and means for moving the log toward or away from the boundary point; wherein, when the log is detected as present both on the supporting means and at the boundary point, the moving means moves the log away from the boundary point; and when the log is detected as present on the supporting means but absent from the boundary point, the moving means moves the log toward the boundary point. 